I agree with WillyNilly. You need to take a different approach. Believe me, I know what of I speak.
It might damage the friendship temporarily but if your friend likes you as much as you do her I don't think the damage will be bad nor do I think it will be long lasting. By taking the road you currently are on with her you are encouraging her, in a way, to not change. She has you to lean on and to "support" her current actions, and you even provide comfort when it comes to its predictable end. Understand, please, that I am including no blame when I say that you are not only enabling her but you are literally encouraging her.
She might not change now, she may never change. All you can do is change how you react. I think you should take on some of that harshness that WillyNilly mentioned. Or use, as someone else posted, the e-Hell phrase, "What are you going to do about it?" Force her to heal herself; it's the only way she will find the courage and willingness to change whatever she is doing that is making her unhappy.
After all, the classical definition insanity is, I believe the saying goes, doing the same thing and expecting different results. That applies not only to her behavior but to yours in the way you are "helping" her. (Please understand I am not saying anyone is insane here, only that repetition begets repetitious behavior.)